<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>过度曲线</title>
    <style>
        .box{
            width: 80%;
            margin: 100px auto;
        }
        .box .btn{
            display: block;
            margin: 0 auto;
            width: 100px;
            height: 50px;
            background-color: powderblue;
            border: none;
            border-radius: 30px;
            line-height: 50px;
            font-size: 15px;
            transition: 2s;
            /* transition-timing-function: linear;   匀速改变*/
            /* transition-timing-function: ease;   默认值，是先变快，后变慢*/
            /* transition-timing-function: ease-in;  先慢，后快 */
            /* transition-timing-function: ease-out;   先快，后慢 */
            transition-timing-function: ease-in-out;  /* 先慢，中间快，后慢 */
        }
        .box .btn:hover{
            width: 200px;
            height: 100px;
            line-height: 100px;
            font-size: 30px;
            background-color: burlywood;
        }
    </style>
</head>
<body>
    <div class="box">
        <button class="btn">按钮</button>
    </div>
</body>
</html>